Such an apparatus is already known, more particularly from the document FR-A-1 083 665. This apparatus has an extractor with, in particular, two features. In the firing position of the apparatus, the extraction claw is in contact with the collar of the charge; the extractor is mounted for pivoting about a fixed axis.
If, at the time of firing, the case of the charge swells too much, it may become jammed within the barrel housing. In this case, upon opening of the apparatus, the claw of the extractor remains in abutment against the collar of the case of the used charge which has unfortunately become interlocked with the barrel and, since the extractor is fixed to the barrel holder, the operator cannot open the apparatus or can only open the apparatus with substantial difficulty. This is the "hard point" upon the barrel at the time of opening.
With document US-A-2 807 902, another sealing apparatus is known, of which the extractor, mounted upon the breech, is pushed toward the axis of the barrel by means of a ring and which can freely move in translation between two front and rear stops in order to, upon opening of the apparatus, be moved forwardly. As a result of this movement of the extractor, ejection of the case, during opening of the apparatus, is already slightly made easier. However, the hard point is not totally eliminated.